package com.demo;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

public class Demo {
	public static void main(String[] args) {
		Map map = new HashMap();
		String str1 = new String("aa");
		String str2 = new String("aa");
		System.out.println(str1.equals(str2));

		map.put(str1, "aaa");
		map.put(str2, "bbb");
		System.out.println(map.get(str1).equals(map.get(str2)));
		System.out.println(map.get(str2));

		ConcurrentHashMap concurrentHashMap = new ConcurrentHashMap<>();
		concurrentHashMap.put(null, 123);
		Object o = concurrentHashMap.get(null);
		System.out.println(o);
	}
}
